Historically, and to varying degrees of intensity, coal has been an important worldwide economic and industrial energy source. The United States of America enjoys an extremely vast and vital heritage of energy resources in terms of both coal and oil.
Until the advent of widespread and plentiful production of liquid petroleum and natural gas, coal constituted the major source of power required to supply the energy needs of many nations. While oil is still immensely valuable in this country, production is about one-half our current requirements. New discoveries are being made but fail to balance the depletion of existing production.
In the United States the shortfall of oil is made up by import from foreign sources. Unfortunately these sources are politically influenced and sometimes inexpertly utilized so that a continuation of vital foreign supplies cannot be assumed.
The known and readily realizable coal reserve in terms of total energy within these United States of America is literally hundreds of times greater than our possible petroleum prospects and are probably sufficient for at least several hundreds of years, even at an accelerated rate of consumption.
Plentiful coal can and will, in time, substitute for scarce and costly oil. It has been done before. Under the duress of World War II the armed forces of Germany were fueled entirely by coal-derived products. Also, the Republic of South Africa is currently, and has been for some time, involved in extensive development of coal derived fuel and related bituminous products.
A major cost factor in the use of coal as an energy source, whether consumer, electric or industrial production, is related to transportation. Currently a considerable amount of coal is being transported from the west (Wyoming, Colorado, etc.) to the near east (Ohio, etc.) and the east coast. In such cases transportation costs equal or exceed the mine source cost of the coal and considerable fuel energy (currently, oil) is expended in the process.
Despite the heavy burden of transportation costs, coal in large amounts is being carried from west to east. Coal is plentiful in the East yet under the present circumstances cannot readily be used. Uncontrolled burning of vast amounts of high sulphur and nitrogen coal presents such an environmental hazard that stern and highly restrictive pollution control measures are mandated. Such mandates place the cost of energy for such fuel beyond present economic realization.
The coal and coke residue resulting from the process described herein is essentially carbon with a pound for pound BTU yield equal to high quality raw or unconverted coal. Its BTU yield per pound is substantially greater than the unprocessed coal thus resulting in a substantial reduction in transport cost on a BTU basis. It is substantially reduced in major pollution generating agents and hence may be used as a mass energy source without prohibitive pollution control costs.
The pipeline transport of coal as a slurry is the subject of intense public debate. If employed, transportation costs would certainly be reduced and large supplies of energy would be conserved.
Various factions for various reasons oppose or support such a notion. An almost insurmountable problem arises out of the need for water as a coal slurry transport means. Coal in the western United States is plentiful but vital water is in short supply there and becoming more so with time. The coal slurry problem is not likely to be resolved under these circumstances.
This socio-economic discussion is included here within the operational outline of the coal process because of its direct bearing on the aspect of energy transportation costs. In a very real sense the widespread distribution of energy also relates directly to this consideration.
Rail transportation of coal is costly both in terms of dollars and oil derived fuel requirements. Pipeline slurry of coal, under the present state of the art, requires transport water utilization beyond reasonable means in many parts of this country as already noted, and in most instances the water would be going in the wrong direction.
On the contrary, coal, when processed as described herein, results not only in valuable petroleum, gas and fertilizer products, but even more importantly a light porous coke of near carbon residue which can be slurried in water derived from the process. This spongelike carbon residue is so soft it can easily be crushed to a fine powder between thumb and finger.
Coal as mined, on the other hand, is crushed or milled to a fine powder only at some substantial expenditure of energy. The milled coal can be mixed with water to form a pipeline slurry. The water cannot be reasonably returned to the source nor can the energy for milling be recovered. It is important to note that mine run coal, even pulverized, is virtually insoluble in water and is not readily wettable. This results in the requirements for considerable amounts of flotation water to form a pumpable pipeline slurry mix.
It is interesting to note that coal when processed as described here takes on a completely different character. The near pure and spongelike coke residue can be pulverized with ease. Being free of oily bitumens and entrained gases it is easily wettable, in fact being hygroscopic to a substantial degree for reasons to be explained. More importantly the water produced during the selective processing is more than enough to produce a highly satisfactory pipeline slurry and this excess water may be used to leach water soluble fertilizer constituents from the porous coke.
It is an object of this invention to obtain water from coal, such water being suitable for most ordinary use as well as in sufficient quantity to be combined with the processed coal as a slurry suitable for pipeline transport.
It is a further object of the invention to produce combustible gas from coal by nondestructive distillation or conversion means, such gas being suitable for on site boiler fuel, pipeline transport or conversion to alcohol.
A further object of the invention is to obtain petroleum type oils, waxes, tars or bitumens from coal in substantial quantities while preventing the pyrolizing of these substances or their reaction with inorganic host minerals, such products being suitable for further refining or fractional distillation into separate hydrocarbon fractions.
A further object is a process for the production of water soluble mineral products such as NPK (nitrates, phosphates, potassium) fertilizer components and sulphur compounds that can be further processed into epson salts, ammonium sulphate or comparable commercial mineral compounds.
Yet another object of the invention is to produce a highly exfoliated, porous charcoal product (coke) from coal that is substantially free of oily petroleum or bitumens as well as being low in inorganic mineral content, especially sulphur and minerals that can contribute to pollution complications as in burning boiler fuel.
It is also an object of this invention to produce a high carbon fuel that can be pulverized with ease and which is water wettable and therefore suitable for the formation of a pipeline transportable water slurry. Another object of the invention is to recover water, coke and gas from lignites otherwise deemed valueless or considered to be a strip mine disposal problem. Another object of the invention is to so process the carbonaceous material that residual unburnable inorganics such as pyrites may be gravimetrically separated and removed.
From the beginning, the various schemes for converting coal have evolved along the consistent pattern of chemical conversion of carbon, water and air. In the absence of some catalyst as yet to be discovered, the thermodynamics of these reactions utilize a substantial portion of the feedstock carbon (coal) and require what is generally considered industrially to be very high pressure and temperatures.
The chemical reactions of these various processes follow the pathway of carbon oxidation to CO.sub.2 and a subsequent high energy reduction to CO. Carbon monoxide, water (steam), and atmospheric and entrained air provide the raw feedstock for further chemical conversion to a host of precusors such as methane and ammonia. Catalytic and hydrogen source reactants further convert the source materials to higher grade synthetic carbon-base fuels and related products.
I have succeeded in substantially altering this traditional method of converting coal to other usable forms. The internal reactions are chemically complex and not yet fully understood, however, the physical means are relatively simple and energy-conserving.
My process preferably involves the concurrent, interrelated actions of time-temperature selection and subsequent refluxing of the evolved various, and generally abundant, volatile constituents of coal, enhancing the ultimate production of lighter fraction petroleum products, pipeline gas, inorganic minerals, water, and a near-pure carbon charcoal residue. The reaction pathway is governed by the time-temperature gradient; fractions are evolved and obtained at progressive points throughout the process.
Another object of the process is to process coal so as to yield up its various volatiles and concurrently to reflux a portion of these same materials with the residual in an unending cyclic manner, employing water, entrained air, gases and vapors evolved by the process. The resulting yield is a wide range of petrochemicals, inorganic minerals, and other hydrocarbons.
The refluxing process is also accomplished at a relatively low temperature through approximately 750.degree. F. maximum, as already noted, and at standard atmospheric pressure. Maximum process temperatures are essentially self-regulated by the boiling points and other phase changes, contrasting strongly with all previous conversion-type processes in which temperatures up to 2000.degree. F. and pressures up to 3000 psi are required.